I have a 1996 dodge avanger 2.0 , standard transmission.
I have a few questions.

1) what does code 12 mean? can someone explain to me what it is and how it might be affecting my car.

2) My car over heats. I already replaced the thermostat, radiator (last year), radiator cap.
It makes a noise that sounds like its coming from the motor. I think it might be the water pump but, Im not sure. When the car is running the upper radiator hose seems like it's going to explode, the lower hose seems fine. The water boils and then it goes to the container and leaves the car without water.

3) When I'm driving the car and I stop at a red light , I shift the car to neutral and then it dies or if I shift from a lower gear to a higher gear it dies unless I press the gas pedal. Also, the "check engine" light goes on and until I disconnect the battery cables and reconnect the light dissapears and the car runs again for a couple of days until the check engine comes on again and the same thing happens.

 

The code 12 means that you have disconnected power tothe car. It takes 50 starts to clear that code.

Your water pump is or might be shot. See if there is any play on the shaft/pully.

Your egr valve or TPS switch is bad